Using noise to blender 2 shaders

I have just set up the texture nodes on my new character bust to give a glow from the cracks in the model.
the base diffuse texture is a muddy brown with dark cracks.
the emission shader gives the cracks a red glow.
I would like a mix of the red glow in some spots and the dark cracks in others.
I figure there is a way to control the mix of 2 texture using a BW alpha noise texture but no matter how I play with the shader I can’t get the “fac” on a mix shader to be controlled by a noise texture.
any advice would be much appreciated.



Thank you

Your basic node tree is correct, but what the hell are you doing with three color ramps in a row like that. Who knows what you’ll end up with. Get it working without any color ramps, then tune it further with one ramp, if you want.

You’re also using your cavity map for like everything. That’s likely to create a situation where your fac doesn’t appear to do anything, as you mix shaders only where the colors change anyways. Just make a new texture, black and white, and hand-paint it, to control the mix factor. Heck, use a half-black, half-white texture to start out with, so that you can tell it’s working, then go from there.

That sould be working, try to plug a noise texture instead of the cavity map that does the mix,
Pug a coloramp set to constant instead of linear before the mix, and adjust the coloramp until you get a correct distribution, then switch back to linear …

A screenshot of the output of the mix factor could help to see if something is wrong. But as some red value looks lighter than the others I guess it’s working.

managed to figure it out for my self.

i needed to remix the diffuse and cavity maps in a mix RBG and then use a noise or voronai texture to control the “fac” for the emission mix. in fact the musgrave texture is most useful for a random mix of black and white for the fac input, with good edges.